1. Field of the Invention
This invention relates to a Schottky barrier diode and a manufacturing method therefor, and more particular to a low forward voltage drop Schottky barrier diode and a manufacturing method therefor.
2. Background of the Invention
Recently, Schottky barrier diodes have been extensively used in a DC—DC converter, a VRM (voltage regulator module), a telecom/server, an adaptor, and a charger. Please refer to FIG. 1 which shows a schematic structure view of a conventional Schottky barrier diode. As shown in FIG. 1, the manufacturing method of the Schottky barrier diode (SBD) includes forming a barrier metal layer 12 followed by depositing a metal layer 11 on a silicon chip 10. The simulation result of a current distribution in the forward conduction mode in the conventional SBD is shown in FIG. 2.
Among all the applications, the SBD is required to provide a low forward voltage drop, low power consumption, and a low leakage current. In order to meet these demands, the forward voltage drop of the SBD must be reduced under a specific operation current range. At the same time, the reverse leakage current thereof can not be increased when a reverse bias is applied. At the present, there are two important methods which are widely used for reducing the forward voltage drop. One is to increase the size of the chip, so as to increase the surface area of the SBD. As the result, the forward voltage drop of the SBD can be reduced for a given current. However, this method also increases the cost of the chip. The other method is to use a barrier metal with a low barrier height, but it will increase the leakage current of the device. It also reduces the reverse blocking voltage of the device and degrades the performance of the device at high temperature. Moreover, the development of a new barrier metallization process is a time consuming procedure due to the sophisticated chemistry and metallurgy at the metal and silicon interface. Furthermore, from the manufacturer's viewpoint, it would be a risk to change the barrier metal because some negative effect might be introduced to the manufacturing control and the product yield, as well as contamination control in the fabrication.
In addition, in some applications, such as the non-insulated synchronization converter and the insulated DC/DC converter, the SBD therein are often integrated with the MOSEFT to improve the efficiency of the electronic system. Please refer to FIGS. 3˜5 which are respectively schematic views of the conventional monolithically integrations of the SBD and the MOSEFT. However, these conventional schemes only provide a limited forward voltage drop reduction due to the limitation of silicon surface area.
Because of the technical limitations and poor electrical performances described above, the applicant keeps on carving unflaggingly to develop “low forward voltage drop Schottky barrier diode and manufacturing method therefor” through wholehearted experience and research.